This invention relates to an improvement in methods for fitting hearing aids and to apparatus or equipment therefor.
In addition, this invention relates to methods and apparatus for testing and determining hearing abilities of a subject or patient, in general.
Advances in hearing aid technology and the technology of testing and fitting these devices have produced more sophisticated and accurate hearing aids as well as more sophisticated software for adjusting these devices. Nevertheless, there continues to be a substantial number of complaints by hearing aid wearers that, despite these improvements, the hearing aids do not function well. A frequently heard complaint of individuals with sensorineural hearing loss is xe2x80x9cI hear, but I don""t understand, especially in noise.xe2x80x9d This is still a principal complaint, even after having been fit with a hearing aid or after the hearing aid has been further adjusted. Indeed, recent observations have been that, despite the availability of better digital devices and the existence of professionals dispensing hearing aids, the overall hearing aid satisfaction rate has remained around 50% for in the past decade or so.
Currently, hearing aid fittings are validated by what are categorized in the industry as subjective and objective determinations. The most popular method for adjusting programmable hearing aids may be termed xe2x80x9csimulated-objectivexe2x80x9d methods.
Common use of the term xe2x80x9csubjectivexe2x80x9d as used in hearing aid industry refers to xe2x80x9cexperiential information to which the subject has xe2x80x98privileged accessxe2x80x99xe2x80x9d (i.e., a third party cannot experience the thoughts of another individual directly, but can merely have access to that information via reports from the subject.) Subjective information is in that respect similar to thoughts, scents, visual and hearing experiences etc., of the subject. Because of the unverifiable nature of such reports, subjective information is generally considered to be of less validity than objective information.
Subjective measures include asking subjects to report the quality of their experience (e.g.: How does that sound?) and having the subject fill out a questionnaire aimed at determining the satisfactory nature of the instrument fitting.
The term xe2x80x9cobjectivexe2x80x9d is used to refer to information that can xe2x80x9cbe measuredxe2x80x9d by a third party, where xe2x80x9cbe measuredxe2x80x9d implies capable of being correlated to a proposed relevant scale. This class includes electro-acoustic measurements, psychometric tests and group clinical experimental results.
Objective measures include electro-acoustic measures by an instrument (e.g., analysis of the physical characteristics of the sound such as its intensity, frequency, etc, presented by the hearing aid in a test box; or as measured in situ with a probe microphone), speech discrimination tests (for instance, repetition of word lists), and sound field audiometry (determination of the improvement in hearing threshold with the hearing aid in the ear).
xe2x80x9cSimulated-objectivexe2x80x9d methods include using computer simulations of what is expected to be the objective electro-acoustic response of the hearing aid, if the hearing aid were fit to an individual with an average size ear, and average acoustic resonance characteristics of that ear. Such methods are carried out with a physical coupling of the prosthesis in only one of many possible alternative couplings regarding canal depth, venting, coupler shape, etc. However, since these values are averages, the simulation normally does not match the response actually present in the ear canal of a particular individual, and in fact can differ by 10 dB, 20 dB or more in certain important frequency regions.
Most of the equipment used today by practitioners presents the objective or simulated-objective information in the form of data, for instance, as instrument readings, displays, computer simulations and the like.
This information is used by the hearing aid dispensing (and/or fitting) practitioner or a test operator to adjust the tuning characteristics of the instrument for each wearer. The more accurate the methods, the more appropriate the adjustments. However, the more objective the fitting methodology, the more technically challenging it is to the practitioner, and the less that methodology tends to be used by practitioners.
Currently, most hearing aid dispensing practitioners fit hearing aids and validate those fittings by the subjective method alone. Those who fit or dispense programmable hearing aids use a simulated-objective methodology. A small percentage use objective electro-acoustic verification methods, and a rare group use in situ measurements. Of those that use in situ measurements a small percentage use digital modulated sound signals that are capable of assessing the performance of the premium digital hearing instruments.
Some instruments are capable of monitoring the acoustic signal in situ in the ear. Some equipment is provided with earphones that may be plugged into the probe microphone system, to allow the dispensing test operator access to certain acoustic signals in the ear canal of the patient.
U.S. Pat. No. 6,056,698 of Iseberg, et al. discloses in concept apparatus for audibly monitoring the condition in the ear of a patient undergoing an auditory evaluation and a method of using that apparatus. This apparatus includes a signal generator for forming an electrical signal based on a condition within an ear (for instance, a probe microphone) and an output for making the signal accessible to an audio transducer (for instance a speaker or earphones connected to a jack on the apparatus). The test operator, in conducting the testing of the subject""s hearing, is thus able to monitor the sounds in the subject""s ear. Specifically, the apparatus allows the test operator to listen during the test for extraneous noises, for instance those produced by activities of the subject such as grinding of teeth. Alternatively, the apparatus may be used by the test operator in advance of testing the subject""s hearing to identify environmental noise, or to listen to the test signal during testing.
Related to the invention is the concept of a hearing loss simulator. Hearing loss simulation has been used both in hearing research experimentation and to approximate for demonstration purposes what it would be like to hear with a hearing loss. In the experimental and demonstration usages, masking noise or a single channel gate (expander) filter, or a graphic equalizer have been used on pre-recorded test materials and presented to normal hearing subjects to compare to hearing impaired subjects.
This invention comprises both apparatus and method for testing hearing and for fitting or adjusting a hearing aid.
In general, the apparatus comprises:
a system for audibly monitoring and testing hearing of a subject by a test operator comprising:
a source of at least one test signal;
at least one probe for insertion into the ear canal of a subject;
at least one first speaker for emitting the test signal into one or both ears of the subject;
a signal generator or probe microphone system, for receiving from the one or both ears of the subject, via the probe, an audible signal representative of a condition within the one or both ears, and for generating therefrom an electrical signal;
an audio transducer for converting the electrical signal into an audible signal;
and at least one filter for filtering out low-level sound tones from the audible signal.
Another aspect of the invention relates to a method of testing the hearing of a subject. More specifically, this comprises:
A method for testing the hearing of a subject by a test operator, comprising:
establishing a threshold hearing level for the subject;
emitting at least one test signal simultaneously into one or both ears of the subject and one or both ears of the operator;
transmitting to the operator a signal from the ear canal or canals of the subject;
filtering low level sounds from the signal transmitted to the operator so as to substantially conform the transmitted signal to the threshold hearing level of the subject, producing a modified transmitted signal;
adjusting the transmitted signal to correspond to the supra-threshold loudness level experience of the subject; and
comparing the modified transmitted signal with the full hearing range of a subject having normal hearing.
The method above can be further used to fit and/or adjust hearing aids by inserting a hearing aid into the ear of the subject after the comparison of the modified transmitted signal with the full hearing range of a normal subject, and by adjusting the hearing aid to compensate for hearing loss.